A few strains of bacteria producing phospholipase $A_2$ ($PLA_2$) inhibitor have been isolated from soil. The most potent inhibitor (named PI-003) was selected through in vitro and in vivo tests. The molecular weight of PI-003 was 1,035, based on FAB-MS, and the constituent amino acid composition was four leucines, one aspartic acid, one valine, and one glutamic acid. The $IC_{50}$ value was $10.1{mu}M$ for $cPLA_2$, PI-003 significantly inhibited carrageenin induced paw edema and writhing syndrome.